Nested undo group with CoreData

Question

I want to add a undo manager to a coredata backed iphone application. When the user tries to add a new object (by tapping on + button) I load a new modal viewcontroller and star

Answer 1

Beginning with your specific questions - Yes, you can manually define the bounds of an undo operation using beginUndoGrouping and endUndoGrouping.

In this case, the undo operation should work whether or not groupsByEvent is set. This is because all the undo groups that are generated by the event loop are nested under your main open undo grouping started with beginUndoGrouping, and as long as you call undoNestedGroup directly after you call endUndoGrouping, it should work. If you are not using the event loop undo groupings, don't worry about it and set it to NO.

To make your changes permanent, close the undo group with endUndoGrouping and call save on your context. The processPendingChanges calls are not needed, and may cause issues in nested groups. If you want clear the undo operations, call removeAllActions on your undomanager after endUndoGrouping - this guarantees the changes will never be un-did.

Use breakpoints/nslog to make sure your begin/end calls are one for one.

If you want your cancel action to be like an 'undo button', you'll have to do the following:

• Move beginUndoGrouping to viewWillAppear

• Call endUndoGrouping in viewWillDisappear

• re-open undo grouping at the end of your cancel action

• re-open undo grouping at the end of your save action

Otherwise, if you leave it as is, make sure you close the dialog in your save and cancel actions, to avoid possibility of endUndoGrouping being called multiple times.

If you have any questions, please comment and I'll update.

Good luck!